1. Department of Preventive Medicine and Environmental Health, University of Kentucky College of Public Health, Lexington, KY, USA.
2. Kentucky Injury Prevention and Research Center, University of Kentucky College of Public Health, Lexington, KY, USA.
3. Department of Biostatistics, University of Kentucky College of Public Health, Lexington, KY, USA.
4. Department of Statistics, University of Kentucky, Lexington, KY, USA.